Apparatus and methods for decoding images

Abstract

A method and system for determining an orientation of a data-encoding symbol, such as a PDF417 bar-code symbol, and for decoding the encoded data. One example method may include detecting an encoded data sequence at a first location of the symbol and at a second location of the symbol. The symbol orientation may be determined at least partially based on the first and second locations. Strings of data encoded in the symbol may then be decoded by processing the strings to generate indices and accessing a codeword array using the indices to look up codewords corresponding to the strings. A match between a string and a codeword may be verified with data in the codeword array.

1. A method for generating a codeword array for use in decoding data, the method comprising:
 using a processor to:
 process a first string of data to generate a first value by performing a function on the string to output an integer, 
 perform a modulo operation on each integer using a number of codewords as divisor to derive the first value; 
 process the first value to generate a first index; 
 store the first value in a first field of a first record in the codeword array, the first record corresponding to the first index; and 
 store codeword information associated with the first string in a second field of the first record. 
 
 
     
     
       2. The method of  claim 1 , wherein the codeword information associated with the first string comprises at least one of a first codeword associated with the first string and an index associated with the first codeword. 
     
     
       3. The method of  claim 1 , wherein processing the string to generate the first value comprises computing a function of the string. 
     
     
       4. The method of  claim 1 , further comprising:
 using the processor to:
 process a second string of data to generate a second value; 
 process the second value to generate a second index; 
 store the second value in a first field of a second record in the codeword array; and 
 if the second index matches the first index, store a sub-index corresponding to the second record in a third field of the first record; and 
 store codeword information associated with the second string in a second field of the second record. 
 
 
     
     
       5. The method of  claim 4 , wherein the codeword information associated with the second string comprises at least one of a second codeword associated with the second string and an index associated with the second codeword. 
     
     
       6. A device for generating a codeword array for use in decoding data, the device comprising:
 a processor that:
 processes a first string of data to generate a first value by performing a function on the string to output an integer, 
 performs a modulo operation on each integer using a number of codewords as divisor to derive the first value; 
 processes the first value to generate a first index; 
 stores the first value in a first field of a first record in the codeword array, the first record corresponding to the first index; and 
 stores codeword information associated with the first string in a second field of the first record. 
 
 
     
     
       7. The device of  claim 6 , wherein the codeword information associated with the first string comprises at least one of a first codeword associated with the first string and an index associated with the first codeword. 
     
     
       8. The device of  claim 6 , wherein processing the string to generate the first value comprises computing a function of the string. 
     
     
       9. The device of  claim 6 , wherein the processor further:
 processes a second string of data to generate a second value; 
 processes the second value to generate a second index; 
 stores the second value in a first field of a second record in the codeword array; and 
 if the second index matches the first index, stores a sub-index corresponding to the second record in a third field of the first record; and 
 stores codeword information associated with the second string in a second field of the second record. 
 
     
     
       10. The device of  claim 9 , wherein the codeword information associated with the second string comprises at least one of a second codeword associated with the second string and an index associated with the second codeword.